| With the rapid development of gold extraction technology in China, the number, size and yield of gold mines are increased, the amount of tailings increased. However, the gold tailings have some characteristics, like the gold resources of gold tailings is very large, and the particle size is fine-grained, processing cost is low, it is a very precious secondary resources, has broad prospects for development and utilization. When we are faced with the problems of environment pollution and lack of resources, looking for an efficient and clean method for the recovery of gold in the gold tailings is very necessary, it will have considerable economic benefits and social environmental benefits.In this paper, gold tailings of Quanshan gold mine in Baotou in Inner Mongolia is seen as the research object，the thiobacillus ferrousoxide is screened from the mine wastewater and gold tailings, according to the results of investigation on mineral composition of gold tailings，researching the optimum conditions of microorganism oxidation pretreatment by using thiobacillus ferrousoxide, to determine microbial oxidation pretreatment effects on the subsequent thiourea leaching gold, then researching the optimum of thiourea leaching gold, and studied the effects on microorganism oxidation pretreatment and thiourea leaching gold of ultrasonic also, finally, we get the biggest recovery rate by using microorganism oxidation pretreatment and thiourea leaching with the flotation together. The study include four aspects:1. The study of microorganism oxidation pretreatment. Researching the effect of inoculation quantity, pretreatment time, ore particle size, water quality, strain acclimation culture, the test results show that: microbial oxidation pretreatment can improve leaching rate of subsequent thiourea leaching test gold, using tap water configuration9K liquid medium, then mix with tail mineral powder, liquid to solid ratio2:1, inoculation quantity15ml, after5d, leaching rate of subsequent thiourea leaching gold can reach to50.54%, higher than leaching rate of without pretreatment experiment27.26%, and the purity of thiobacillus ferrousoxide is higher after subculture, the growth ability of thiobacillus ferrousoxide is stronger after acclimation culture, more suitable for microbial oxidation pretreatment application.2. The study of the influence of ultrasonic effect on microbial oxidation pretreatment experiment. The test results show that:(1) Ultrasonic effect on microbial pretreatment process can strengthening the effect of microbial pretreatment，leaching rate of subsequent thiourea leaching gold is improved, it is higher than leaching rate of without ultrasonic4.73%, can reach to60.4%;(2) During microbial oxidation pretreatment process, ultrasonic processing3days and ultrasonic transmission power reach to90W is optimum condition.3. The study of thiourea leaching gold. Researching the effect of liquid to solid ratio, leaching temperature, leaching pH, thiourea concentration, Fe2(SO4)3mass fraction on gold recovery in the tailings, the optimum conditions obtained are as follows: liquid to solid ratio2:1, leaching temperature25℃, leaching pH2, thiourea concentration15g/L, Fe2(SO4)3mass fraction0.4%, ultrasonic power90W, ultrasonic treatment time40min, and the leaching time60min. With these conditions, leaching time is reduced greatly, leaching rate of gold is improved, reach up to62.4%.4. The flotation-microorganism oxidation pretreatment-thiourea comprehensive test of recycling gold. We get gold concentrates by flotation first, then microbial oxidation pretreatment, using acidic thiourea method to recover the gold finally, the ultimate recoveries of gold reach to60%, higher24%than the ultimate recoveries of gold without pretreatment. |
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